ADELE-SPRITE

ADELE / SPRITE is a field campaign combining two separate research projects at the same location at the same time. The project will deploy out of Melbourne, FL. The ADELE part will operate during the day studying gamma rays near convective storms. The SPRITE part will operate at night time studying formation of sprites over the thunderstorms up to 200 km away from the flight track. Also contains instrument for testing as part of HEFT-09.

SPRITES

This proposal is submitted to the NSF CEDAR program in collaboration with Dr. M.G. McHarg, US Air Force Academy. The overall goal of the proposed research is to continue joint work on high time resolution imaging and spectroscopy of sprites.

The GI/UAF work will concentrate on high-speed spectroscopic observations primarily in support of the PhD thesis work by graduate student T. Kammae. Under the earlier grant we demonstrated our ability to record optical spectra with millisecond resolution. Analysis of the spectra indicates that there is an altitude variation in the spectra which may indicate an altitude variation in the physical processes creating the optical emissions in sprites. Surprisingly, we have not observed any ion emissions, which, if current sprite theories are correct, must be there. It is likely that the spectra obtained so far are from the “afterglow” region and not the active streamer heads. We now know that the streamer heads are very bright and that they are essentially point sources of light. Thus slit less spectroscopy, i.e. imaging through a diffraction grating similar to what is often used in astronomy can be used. This will greatly enhance our chances. For the observations we will use the USAFA Phantom-7 camera rather than the GI/UAF slit spectrograph used previously, which is less suited for these observations. We used the Phantom camera as a slit less spectrograph with very good results on the StarDust satellite re-entry in January 2006 and evaluation of that data suggests that it should work well for sprite streamer heads.

The proposed effort is divided into an observational and an analysis part. Two-week observation campaigns are planned for each year. For budgetary purposes we assume observing from the Langmuir Laboratory, a lightning research facility near Socorro, New Mexico. However, we have also used WIRO, an infrared astronomical observatory south of Laramie, Wyoming, and may go there. Both sites offer a high altitude site with excellent viewing conditions over the Mid-West Prairie.

As mentioned above the analysis will concentrate on the spectral characteristics of sprites aiming at identifying the physical processes involved. Of critical importance is the spectrum of streamer heads which so far has eluded us. The analysis will primarily be done by graduate student, Mr. Takashi Kammae. He has developed a model for the spectra that compares well with observations. This work will be central to his Ph.D. thesis. Mr. Kammae is expected to graduate in Year 2 of this effort and upon graduation we anticipate to start another graduate student.