SonotaCo.JP

[ada]

続いて8mmの分です。

[Lightningwizard]

Thanks for showing this interesting event!
This is my interpretation of the flash sequence: it appears that the initial +CG flash that triggers the sprite was initiated by a leader coming from elsewhere in the storm. After this positive charge removal (we cannot see where exactly it was, overexposed) the negative leader channels inside the cloud remain conducting and a new positive leader (left side of the image, slow and no side branches) comes down, makes a new +CG tapping from the region lit in the center of the image. But the previous +CG that produced the sprite already removed most of the charge, so this new one is not as energetic. It deposits negative charge along the channels inside the positive charge layer. This causes new negative leaders to spread from this region in both directions, a bright arm goes with speed estimated at 100 km/s to the left, this activity may be connected to another weak +CG in the distance. Possibly a vertical discharge between two layers inside the cloud occurs as final redistribution of charge.
A very complex sequence, and more definite conclusions are only possible with intracloud lightning mapping systems, high speed cameras and electric field measurements.

Oscar

[SonotaCo]

Hi Oscar
Thank you for comment. Very interesting. It may be reasonable.

[Lightningwizard]

(this post was incomplete)

[Lightningwizard]

Hi SonotaCo,

the most likely polarity of the horizontal leader is negative, it obeys commonly observed speeds and shows some branching. We cannot be totally sure though. Negative leaders move through positive charge layers, and these are extensive in the stratiform region of MCS storms and in winter thundershowers. We cannot see the end of positive polarity I think, it may be deeper in the cloud and/or far away.

About the situation of your second scheme, of the sprite:
Positive charge is removed from the stratiform region of a MCS, at about 5 km altitude (or near 0 degrees C). Free ions move continuously under changing electric fields to compensate them, and their mobility is greater with altitude, so electric fields can only exist for very short times in the mesosphere (40-90 km altitude, about 100-0.1 ms respectively). So only when all of a sudden electric charge is removed within such short time, a field can exist at these altitudes. For removal of positive charge, the change is effectively the same as inserting a negative charge. So only the charges that change create electric fields, not the static ones. And only large enough removals will allow breakdown in the mesosphere. Downward streamers of the sprite thus have positive polarity and upward ones (in carrot sprites) negative.

The invisible move of ions and electrons from the free space above the storm downward and upward should indeed happen but would not cause a jet (maybe it could initiate a palm tree/troll event by runaway breakdown if the fields there are very strong). Jets occur in different situations, from the top levels of the core region of storms, as a response to a charge imbalance created by CG discharges, in presence of strong screening layer charge (as explained by Krehbiel et al. in Nature, 2008). Gigantic Jets come from the central charge of a storm.

Oscar

[SonotaCo]

Hi Oscar
Thank you for detail explanation. I learned much.

[masuzawa]

[masuzawa]

[SonotaCo]

測定ありがとうございました > masuzawaさん
ada さんの click とあわせて SA2 で処理しました。
対応関係は Nagano1 の1,2,3,4,5,6 を chiba2 の 3,4,1,2,5,6 に対応させました。
丁度イベントを東西からみる形になっているので、左右が逆になるわけです。
非常に惜しいことに、今回のイベントはほぼ千葉と長野を結ぶ一直線上に発生しており、交差角が殆どなく、三角測量の精度が出ません。
が およその位置は当初adaさんが示された地点でほぼ間違いないようです。

で、驚くべきは、 長野からはスプライトを含んだ全体が1つのスーパーフラッシュとして記録されていたということが確実になった点です 。
これは従来からのスーパーフラッシュの謎の1つの答えになっていると思います。
やりましたね。

あと、スプライト発生直後の3フィールドの3カメラの記録を連結してみました。
これはフラッシュと稲妻の関係の貴重な記録になったと思います。
Tokyo1がイベントの瞬間ホワイトアウトしていたのが、なんとも残念です。
もう少し東で発生すれば、感度の違うカメラの視野に入ったのですが、本当に残念でした。