Wednesday, August 17, 2005

False colour reveals interesting movement in sprite

Just an idea that came up when seeing two nearly identical frames that have been recorded of the same sprite that we just captured this night. The above image is a false-colour composite of two frames separated by 40 msec. The first frame is given the red color. The second frame the green color. It appears that the illuminations have slid upwards along the bottom tendrils during this time. Note that the same happens at the top of the sprite.

Sprite!! Night 16-17 August!

Less than an hour ago, at 2306 UT (1:06 local time), one sprite was caught over northeastern Spain by the Pic du Midi camera, and it was very close to the camera!

Here is the original image for you:

The image has been recorded by the wide field camera (32 degrees) which was pointed in this direction 5 minutes before the sprite happened: 2005-08-16 23:01:06 : Pan: 159.9 Tilt: 28.8 degrees (the true values are slightly different). The sprite must have appeared the angular size of your fist if you stick it out at arms length!
A +24.5 kA lightning flash was detected at the same time, at 41.99 N and 0.83 E. The 10.2 degrees narrow-field camera captured a part of the lower branches. In order to get a possible new sprite centered in both views, I adjusted the camera to a higher tilt and more to the left, but it got cloudy in the minutes right after the sprite, unfortunately.

Tuesday, August 16, 2005

Thunderstorm Outlook: Tue 16 - Fri 19 August

These days we can expect to see more and more thunderstorms to develop over northern Spain and the southern half of France. Storms may finally come very close the cameras again, especially Pic du Midi, which may allow detailed closeups if sprites occur - but more likely this generates cloudiness (models forecast 35mm of rain over Pic du Midi tonight between 20:00-02:00!)

Monday, August 15, 2005

VLF perturbations associated with the 29 July sprites

During the sprite events captured on the 29th of July the parent cloud-to-ground lightning discharges were located close to the GCP-s of the NAA (24.0 kHz), HWU (18.3 kHz) and HWV (20.9 kHz) transmitters to the Crete VLF receiver (see the picture).

Early VLF perturbations have been observed in the amplitude data of the HWU transmitter for 8 sprites (out of the total 10), among which 4 have also been seen in the amplitude and/or phase of the NAA signal. There were no perturbations associated with non sprite-producing CG discharges.