Databases for THEMIS and GEOTAIL Magnetopause

Crossings at GSFC

Vladimir Kondratovich

David G. Sibeck

• Data from THEMIS and GEOTAIL streams are selected for time intervals when the probes are near the nominal magnetopause

• Data are transformed into the Boundary-Normal Coordinates (convenient to analyze the transfer processes)

• THEMIS data streams are merged in order to offer the best time coverage

• Cutoff potential is determined and applied to data.

• Plots appear on SPDF GIFWALK for quick viewing. Links for FTP download of the scalable graphics (PS and PDF) and merged and transformed data (compressed ASCII) are also provided.

Data Selection and Processing

Boundary-Normal Coordinates (BNC), called also LMN-coordinates, are convenient tool in description of the boundary problems (in part, FTEs and magnetopause crossings).

In our case, the boundary is magnetopause. Standard plots use nominal magnetopause, while transformation to dynamic BNC is available for research case-by-case plotting.

THEMIS PROBES

e

d

c

b

a

Event-driven data (no continuous time coverage). THEMIS data products are merged for better coverage. This forms a unique dataset (not provided by THEMIS)

ASCII: 32 MB, ZIP: 7 MB

Review Plots

Fields Velocities

GIF: 170 KB, PS.ZIP: 7.5 MB, PDF.ZIP: 10.5 MB

1-hour detailed plots

Up to 24 plots

GIF: 130 KB, PS.ZIP: 0.4 MB, PDF.ZIP: 0.5 MB

Magnetopause Crossing Database Structure

Database includes two parts:

1. GIF images allowing quick browsing through the data. Posted at SPDF GIFWALK, http://cdaweb.gsfc.nasa.gov/cgi-bin/dev/themis_walk

2. Data files and scalable graphics available for FTP download from SPDF. Links are given below GIF images.

IDL readers and data and plot descriptions will be provided.

Review PlotsTwo review plots –Fields and Velocities – cover entire time interval when a probe is closer than 4 RE to the nominal magnetopause.

Fields plot show the electron spectrogram, electron pitch angle distribution for two energy intervals, Ne, Tpar and Tper, E and B in the boundary-normal coordinates, separate graph for Bn, and Fourier transforms for B.

Velocities plot shows the ion spectrogram and two pitch angle distributions, Ni, Tpar, Tper, velocities from ExB and moments in BNC and the Fourier transform of the latter. The plot also shows the probe trajectory in GSM, its Earth track and color code for data (shown as the color bars on the individual graphs).

One-Hour PlotsTwo one-hour plots –Fields and Velocities – show the same quantities as the review plots.

Fields plot show the electron spectrogram, electron pitch angle distribution for two energy intervals, Ne, Tpar and Tper, E and B in the boundary-normal coordinates, separate graphs for Bm and Bl, |B| and Bn, and Fourier transforms for B.

Velocities plot shows the ion spectrogram and two pitch angle distributions, Ni, Tpar, Tper, velocities from ExB and moments in BNC and the Fourier transform of the latter. The plot also shows the probe trajectory in GSM, its Earth track and color code for data (shown as the color bars on the individual graphs).

Scalable Graphics One-hour plots are primary research tools. They can show fine details on the scale of seconds (the probe spin period is about 3 s).

Research routines (for specific event study) can use the finest resolution data offered by THEMIS as well as dynamic magnetopause models with variable time resolution and lag.

Work in Progress

• Catch up with THEMIS data by the end of the year (also, post the “hot” dates as soon as possible).

• Hook up Research and Collaboration Tool to GIFWALK display.

• Implement the logical trees for best data selection using newly-available data quality flags.

• Automatize some pattern detection in the BNC.

• Now soliciting input for inner magnetosphere survey plots.