List of MISETA working group meetings:

• 1999: Jan 8-9, Clemson University, SC
  
• 1998: Jan 16-17, Clemson University, SC
  
• 1997: Feb 20-21, Boston University, MA
  
• 1995: December, special session at fall AGU, San Francisco.
  
• 1994: Oct 14-15, Hanscom AFB, MA.
  

Summary of CEDAR/MISETA 98 Workshop

MISETA hosted a two-hour CEDAR workshop to review progress since the winter workshop held at Clemson in January 1998. Attendance was excellent with all seats in the room occupied. About 25 students were present in addition to about 40 scientists who all received baseball caps bearing the MISETA logo.

The MISETA program has been funded to continue operations through solar maximum in 2001. The MISETA investigators and students reviewed new results in observational, analysis, and modeling activities centered on data obtained by the MISETA instruments at Ancon, Arequipa, Tucuman, and Jicamarca, in Peru. The reviews began with Cassandra Fesen who discussed recent results of NCAR TIEGCM modeling of the equatorial thermosphere. By reducing the electron density at the lower boundary, the model now reproduces the general seasonal and solar cycle trends observed in the F-region vertical ion drifts, particularly the pre-reversal enhancement which occurs just after sunset. The cause of the feature is under investigation. A careful comparison of observations and model predictions for October solar cycle minimum is underway to examine the current capabilities of the model.

Cesar Valladares summarized the analysis of Ancon scintillation drift measurements combined with Arequipa FPI observations. The data suggest rather strongly that the probability for the development of spread-F and scintillations will be larger when zonal winds in the early evening are weak than when they are strong (i.e., speeds greater than 50 m/s). This appears consistent with modeling results provided by Fesen. A JGR paper summarizing these results is being prepared this summer with submission planned for the fall.

Using information provided by Rick Niciejewski, John Meriwether summarized the status of the Michigan Fabry-Perot interferometer located at Carmen Alto. The instrument is currently not operational but a substantial amount of usable data was acquired during the August-September 1997 period that overlaps simultaneous measurements from other MISETA instruments. Meriwether also pointed out an interesting aspect of the Arequipa FPI results for this same time period: observations show a momentary reduction in the zonal wind shortly before the "brightness wave" (BW) passes through from south to north. He suggested that this zonal wind reduction was caused by the "back pressure" of the midnight pressure bulge associated with BW events. Mendillo and his students summarized their analysis of all sky images from Arequipa and Tucuman. Their aim is to deduce the drift speeds of airglow depletion events for both sites to determine whether the zonal winds are weaker for the higher latitude station. Theory suggests that this would be true since increased ion drag associated with the enhanced electron densities in the Appleton Anomaly should reduce the neutral wind speed. Analysis of BW events for both stations is continuing. David Hysell reviewed the ongoing series of Faraday temperature observations obtained at Jicamarca with the incoherent scatter radar. The results are looking very reasonable with very good error bars. The measurements can be downloaded from his Web page or by a link from the MISETA Web page (addresses below). The group intends for all the data and model simulations of MISETA campaigns to be available through the MISETA webpage. This activity is ongoing. Finally, plans for a major MISETA campaign in April, 1999 were discussed to support the Terriers satellite scheduled for launch this fall. The next MISETA workshop will be held at Clemson this coming winter.

Summary of Clemson 98 Workshop

Our meeting started with an assessment and summary of general plans for MISETA over the next three years, a period of strongly increasing solar activity. significant years to obtain observations since solar activity is expected to increase from the current weak range of F10.7 ~ 75 to 100 to over 200 in the year 2001. All MISETA systems have been funded to continue activity. These include the Arequipa and Ancon observations of airglow images, thermospheric winds and temperatures, ion drifts and scintillation activity levels. These results are to be supplemented by the JRO observations of electron density and ion and electron temperatures during campaigns that will take place every three months. Fabry-Perot neutral winds near the Appleton anomaly and all sky imaging observations will be obtained from Carmen Alto and scintillation drift measurements from Antofagasta in Chile. Digisonde observations will be obtained continuously from Jicamarca (Peru) and occasionally from Antofagasta in Chile. Tucuman imaging observations will also be taking place simultaneously with Arequipa and Antofogasta (Air Force imaging).

After reviewing the current ensemble of available data, we identified four projects which should yield results in the very near future. The list is appended at the bottom of this message. We agreed that reports on these four projects would be the main agenda items at the CEDAR/MISETA workshop in June.

We also discussed the following:
- publication plans re these studies. We decided to wait until the CEDAR meeting to see how the work was progressing to decide if they should all aim for a common completion date.

- plans for the next JRO/Faraday campaigns in June 1998 and October 1998. (Unfortunately, it appears that the January results for 1998 were flawed due to a software problem. ) In general, we found ourselves impressed by the quality of the JRO Faraday observations. Dave Hysell described all of the efforts that JRO put into making this achievement possible. Meriwether has sent to NSF a letter indicating that we were pleased with the quality of the results now emerging from the JRO Faraday run measurements.

- the MISETA web site. Meriwether has submitted postscript data files for 96 and 97 FPI results to Fesen. Mendillo indicated that BU would look into what it could provide to characterize the imaging results. One possibility is a summary plot that represents the plot of the meridional scan slice through all of the images. Boston College will provide scintillation drift data to be posted on the Web site.

We will meet again at CEDAR and then again in the winter of 98/99. We agreed that we should meet roughly every 6 months. Meriwether would be pleased to host the off-CEDAR workshops at Clemson. However, the alternative of rotating the meeting place among the various PIs' home institutions might be more attractive to the group. We will discuss this further at the CEDAR/MISETA workshop.

1. TIEGCM validation at equatorial latitudes during solar min (Fesen)

The observations over the past three years (1995-1997) represent valuable measurements of the equatorial thermosphere. It is timely to consider publication of these results, especially with a comparison to the predictions from the evolving NCAR general circulation model. We agreed to focus upon the results for the period of September-October 1996, representing solar minimum conditions, that utilizing results for 6 nights (3 active, 3 quiet).

The critical issues regarding the TIME-GCM performance are the accuracy of the model calculation of the ionosphere which depends heavily upon the representation of the neutral densities (e.g., the ratio of O to moleculars). The analysis draws upon MISETA observations of winds, temperatures, and airglow brightnesses; calculations of the 630 nm brightnesses may yield valuable information on the question of neutral composition since the 630 nm brightness is somewhat sensitive to the N2 quenching which depends in part upon the O/N2 molecular ratio. We will also compare how the NCAR composition compares with the MSIS model. Meriwether will undertake to produce an average pattern of nighttime winds during this period. Mendillo will examine the question of sky brightnesses, and Valladares will compare the ion drift measurements with Fejer's model to determine how

2. Identification of scintillation sources at low latitudes: BSS vs. Bubbles/Plumes (Valladares)

role of multi-diagnostics

observations (1996-1997): case studies of particular days.

Use the following:

• JULIA
• spaced receiver
• imager
• GPS

3. Ion-neutral coupling and dynamics (Meriwether and Valladares)

issues: dynamo vs penetration electric fields, using both single sites to study statistics and the ensemble of measurements to study the latitude pattern

how well coupled are the neutral atmosphere and ionosphere in the E/F region dynamo regions?

case studies of how neutral winds and ion drifts compare

observations to include:

• FPI and spaced receiver at Arequipa
• imagers at Arequipa and Tucuman
• FPI and spaced receiver at Antofagasta

comparison of depletion drifts at two latitudes-> Tucuman and Arequipa all sky images (Mendillo)

comparison of Chile and Arequipa neutral wind measurements (Meriwether)

comparison of Chile and Arequipa ion drift measurements (Valladares)

examination of differences of Un-Ui, isolate special cases where Ui> Un (Meriwether and Valladares)

examination of statistics of Un,Ui for nights of spread-F and no spread-F activity (Valladares and Meriwether)

4. MTM related sources and effects (Mendillo)

issues:

• day-to-day variability
• latitudinal extent of the feature
• poor representation in the TIEGCM
• is it in TIMEGCM/CCM?

• FPI and imager, Arequipa
• imager, Tucuman
• imager, Arecibo
• satellite data (AE; others?)
• Faraday Tn data?

Summary of CEDAR/MISETA 1996 Meeting

The MISETA workshop session at CEDAR met on Friday afternoon with a substantial turnout of about 50 people that dwindled as the afternoon waned into evening. A summary of the day's activities follow, written by John Meriwether. In introductory remarks at the CEDAR 96 MISETA CEDAR workshop the MISETA coordinator John Meriwether suggested that we hold a major workshop in the next year similar to the type held at Peaceful Valley for other CEDAR initiatives. The consensus seems to be to hold this, a 2 or 3 day workshop, for a period in late March, 1997, that would coincide with the university spring breaks. This conference would enable us to review results for MISETA II and MISETA III (observing campaigns held in the spring and fall of 1996), consider further results from MISETA I, and to make plans for the MISETA renewal proposals to NSF to be submitted to NSF in May, 1997. Meriwether suggested that the workshop be hosted at Clemson University where there is good convention facilities that would support a meeting of 100 persons rather easily. The immediate neighborhood offers an excellent 18 hole golf course for those interested in such activities. Getting away from winter conditions may sound attractive to the New Englanders.

In regards to the question of renewal funding, in the last year MISETA has been productive: a special session at the AGU last December, a total of 11 journal papers, another campaign in hand with reasonably good data, and a third campaign in the works. Also, the work that remains look to be substantive. The Peru/Chile combination was delayed a year through no fault of our own, and most of the results from the second Peru/Chile effort will not have been analyzed by the time of next May.

At the CEDAR workshop meeting reviewed the list of MISETA science goals that were originally set out. We have a good list of milestones of achievements that we can point to as well as significant goals that remain to be realized. A suggestion was made to broaden our charter to include studies of longitudinal differences in equatorial aeronomy, one that is very much an issue. There is also the question of coupling to the lower atmosphere and, moreover, the possible changes in the morphology of spread-F that would appear with changes in the solar flux expected over the next three years that deserves study. Meriwether feels that the March 97 meeting should spend some time exploring these issues as to possible continuation paths for our initiative.

Meriwether also discussed at the workshop the matter of whether the MISETA effort should be split up into two parts, one pertaining to the large scale aeronomy issue and one pertaining to the question of spread-F and scintillation studies. The consensus of our discussion was that we should stay together and not split up. There is enough room under one umbrella for both thrusts. People, Michael Mendillo particularly, thought that the momentum of MISETA would be diffused if the initiative were split up into two parts, and there did not seem to be any real justification. The comment that one thrust might be funded by CEDAR and the other funded by Space Weather was presented to the audience and discussed. The general feeling was that in spite of the fact that people in the audience may receive their funding from separate sources including the Air Force, we should all still stick together.

The series of talks at the workshop centered around the two major themes of large scale thermal structure and the issue of scintillation and spread-F activity. We heard from Colerico re the imaging observations for April, 96. Airglow depletion events and brightness waves were seen frequently throughout the month of April. The weather was reasonably good for the second half of April. Only the nights of 15/16, 16/17, and 19/20 of April were cloudy for the whole night; the other nights from the 10th to the 24th were generally clear though drifting clouds may have obscured observations for an hour or two. Early evening periods were generally bad. Depletions were seen on the five nights of 11/12,12/13, 14/15, 17/18, and 21/22 April. Brightness waves (MTM-instigated events of airglow enhancements) were seen for the six April nights of 12/13, 15/16, 17/18, 18/19, 20/21, and 21/22. Comparison with previous years showed more brightness wave waves (6 vs 4 and 2) and about the same number of depletion events.

Meriwether (Clemson University) reported on the FPI modifications that took place to eliminate the OH contamination problem that were affecting FPI measurements of temperatures for weak 630 nm signals. Meriwether also noted that the old laser calibration source has been replaced with a source that is frequency stabilized and expected to exhibit less drift than the commercial instrument previously used. The April 96 data shown showed a clear indication of the midnight temperature anomaly in the zenith observations that extended over several hours. Observations were obtained throughout the MISETA period.

Killeen (U. of Michigan) reported on the progress for the installation of the Michigan FPI in Chile. The trailer has arrived but the installation will not be complete until toward the end of July. Calculations show how bistatic observations within a common volume would be possible with the Arequipa FPI as the overlap is quite substantial. Such measurements will provide definitive measurements regarding the magnitude of vertical winds. Biondi (U. of Pittsburgh) has worked out the angles and positions for such common volume measurements of thermospheric winds by both FPI observatories.

Dave Hysell (Clemson University) reported on the JRO observations that were made during the April MISETA II campaign. Observations in the Faraday mode (Ne, Te, Ti, N(O+), N(H+) were taken on the sequence of four nights from the 15/16,16/17,17/18, and 18/19 for times running from typically mid-afternoon (16 LT) to 03 LT. Two more nights of data were obtained on the 22/23 and the 23/24; unfortunately data were obtained only to 2130 LT for the last night. These nights are thought to have a bit of contamination as the antenna was moved away from the perpendicular direction to B but perhaps not far enough. Two additional nights in May on the 10/11 and the 14/15 provided further measurements (data for the whole night was collected on the 14/15 but only to 22 LT for the 10/11) with the antenna angle well away from perpendicularity. The May data sets did not exhibit any indication of Te < Ti for nighttime between 200 to 450 km, and the values of Te appear to be around 750 to 800 K, which is consistent with the results obtained by the Arequipa FPI during this period. (Simultaneous FPI measurements are available but not reduced as yet). Examination of the radar data did appear to show a slight increase of Ti near midnight near 300-350 km, a possible indication that the anomaly did occur overhead of JRO. (However, the possibility of H+ contamination must be examined before a final conclusion is made). Thus, it appears that a combination of the FPI, BU imaging, and JRO temperature observations would represent a useful data set for the study of the midnight temperature anomaly. Hysell indicated that the results are available for inspection and study on the WWW site: http://landau.phys.clemson.edu/faraday/faraday.html

Before the start of the Faraday observations, three nights of coherent scatter observations were obtained on the April nights of 11/12, 12/13, and 13/14. The first and the third showed strong indications of radar plumes, but no drift measurements were available for the first night due to equipment problems. Results on the scintillation drift measurements from Ancon were presented by Valladares (Boston College) to show that significant spread-F activity took place on an occasional basis up to about the 19th of April. Drift measurements were available for nights of: 8/9, 9/10, 11/12, 12/13, 14/15, 15/16, 16/17, 17/18, 21/22, 23 (morning 08-09), 24 (07-10), and 27 (01-03). Valladares compared results between the Fejer JRO model of zonal drifts with the scintillation drift measurements and noted that where there was a discrepancy, it could be explained on the basis of an argument that the ionosphere was higher at the time and therefore, there is less ion drag and a higher ion drift speed.

Friedman (Arecibo Observatory) presented FPI results that were obtained during the April period. The best results were obtained towards the end of the MISETA period due to the weather conditions. Unfortunately, the temperature values were considerably higher than expected, i.e., typically around 1100 K rather than the expected 800 K suggesting that the laser calibration of these results need to be reviewed.

S. Basu discussed further the need to interrelate the neutral wind measurements with scintillation drift measurements to compare the degree of coupling between the ionospheric plasma and the neutral atmosphere. He reported on the Phillips Laboratory plans for the Chile October campaign effort, which will involve Digisondes, scintillation drift measurements, all sky imaging systems, and a 50 Mhz radar system. These measurements will be obtained at a site near that of Antofogasta. An extension to previous capability will be the coverage of GPS frequencies in the scintillation observations. A matter that came up during this discussion was the question of how to observe the northern Appleton Anomaly to supplement the observations planned for Chile (Phillips Laboratory) and for Tucuman (BU). Killeen mentioned that Michigan had an imaging system that might be available for this purpose. Mike Taylor (Utah State U.) indicated that their imaging system that was operated in Brazil to observe F-region effects would be observing in Chile not only the F-region but also to look for waves in the OH and OI airglow emissions. Some discussions of possible stereoscopic effects ensued but the baseline separation between these two imaging systems is likely to be too small for a significant height determination capability to result from any stereoscopic images. Perhaps this issue should be looked into with more care.

Bela Fejer (Utah State Univ) showed results from the statistical modeling of the neutral winds and plasma drifts. Cassandra Fesen (U. Texas, Dallas) reported on the latest work on the calculations of the midnight temperature anomaly. These results show that the temperature anomaly can be simulated to some degree if the E-region electron density were reduced to levels below that of 10E4 el/cm3. Observations, especially those of the old ionosondes that scanned to frequencies as low as 0.25 Mhz, support such low E-region densities in the equatorial ionosphere.

Erhan Kudeki (U. of Illinois) presented further results from the MISETA I campaign and suggested that observations in the interferometry mode need not continue unless there are indications of interesting activity going on that might be available from the observations in the incoherent scatter drift mode. Otherwise, just too much data can be collected that would not be analyzed and examined closely. We then heard commentary from Bodo Reinisch (Univ. of Lowell) and Jim Scali (Univ. of Lowell) about the contributions that the Digisonde at JRO can make to the day to day observations of ionospheric variability at Jicamarca and elsewhere. Scali noted the potential for new physics to enter into the understanding of the ionospheric behavior for the Far Eastern sector.

We really did not have enough time to do justice to either of these two themes, even though we had four hours. The problem in part is simply that the new data that represent the measurements of MISETA II have yet to be assimilated and intercompared between BU, Clemson/Pitts, the Ancon/BC, the Lowell Digisonde, and JRO radar observations. The work of coordinating the analysis activities need to take place off line, but with the data just in hand, it was not possible to do more than take note of the facts in regards to the observations. The bottom line is that all instruments worked, there were quite a few clear nights within the April period, and there were considerable scintillation activity/spread-F for much of the campaign. The temperature comparison between JRO and the FPI appears reasonable with both instruments showing values around 800 K.

The discussion at the close of the MISETA workshop centered around the question of observing plans for JRO in terms of the particular mode that would be used. The final recommendation was for the MISETA III period to include 5 nights of incoherent scatter zonal drift measurements between 28 September and 7 October (excluding weekends), and the ABC effort will include 5 nights of Faraday mode observations from 8 October to 12 October. The time after 12 October to the end (perhaps another week or two) would be in the Julia mode. When the radar is not operating in the incoherent scatter mode (between 28 Sept to 7 October), it is my understanding that Julia would be pressed into service as there are no major antenna changes required to switch from JRO to Julia and vice versa. The advantage of the incoherent scatter mode is that zonal and vertical drift measurements would be attained but without the huge amount of data that the interferometry mode collects. It would be possible to switch into the interferometry mode should anything of great interest comes along. All of the information that is required by optical or scintillation equipment for comparison with the onset of spread-F activity will be available from the incoherent scatter mode. Rudy Wiens (York University) mentioned that WINDII on the UARS spacecraft may be able to support the MISETA III observations by providing observations of lower thermosphere winds with the green or red OI emissions. He has examined this matter further and it looks as if the overflights of UARS in the South American region did place in the mid-evening hours for the April MISETA II campaign period of 10 April to 24 April. However, possible support for the MISETA III period does not look favorable because the satellite is scheduled for a Yaw maneuver near the 10th of October. This means that all instruments are switched off in the two weeks period prior to this time. However, perhaps something can be done about this timing to improve things in connection with the MISETA III observations.