Monday Seminar Talk (short) 17 November, 2003
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Transcript of Monday Seminar Talk (short) 17 November, 2003
Monday Seminar Talk (short) 17 November, 2003
Taro Morimoto
Abstract
The solar polarity reversal
The cessation of high latitude CMEs
Close Relationship
- based on the observations for cycles 21 & 23.
The polar crown filaments need to be removed before the poles could acquire open field structure of the opposite polarity.
Because :
IntroductionDisappearance and reformation of polar coronal holes. (Webb, Davis & McIntosh 1984; Bilenko 2002; Harvey & Recely 2002)
Disappearance of polar crown filaments(PCF).(Waldmeier 1960; Makarov, Tlatov & Sivaraman 2001)
Goplaswamy et al.(2003) Prominence eruptions at high latitudes subsided around the time of the polarity reversals. (From SOHO/LASCO & NoRH observations)
IntroductionUsing CME data of cycles 21 & 23, they tested how CMEs are intimately connected to the mechanism of polarity reversal.
Data
21
CME
Solwind
23 SOHO/LASCO
Prominence Eruption (PE)
Nobeyama radio heliograph
Kitt Peak magnetograph measurements for polar region magnetic field strength
PE and CMEs
epochs of cessation of HL activity (north; : south)
HCS
HCS Max. excursions of heliospheric current sheet. (from Wilcox Obs.)
North-south asymmetry in the high latitude (HL) activities.
CME occurence rate
HL : High Latitude ( 60°) [PCF-related = 1159 CMEs]≧LL : Low Latitude ( 40°) [AR-related = 4607 CMEs]≦SSN: daily Sun Spot Number
CME peakSSN peak
Cycle 23
01
3
3
05 1003 10month:
North South
Northern HL(NHL)
HL CME peakmid/99 A rapid increase
03/00 – 09/00 A broad maximum
Polar field reversal: 10/00 from data
02/01 (Bilenko 2002)
05/01 (Durrant & Wilson 2003)
PCF disappearance10/00 (Harvey & Recely 2002; Lorenc, Pasorek & Rybansky 2003; Gopalswamy et al. 2003)
Disappearance of PCF
Cycle 23
01
3
3
05 1003 10month:
North South
Southern HL(SHL)
HL CME peakmid/99 – 03/02
Polar field reversal: 05/01 from data
09/01 (Durrant & Wilson 2003)
01/02 (Bilenko 2002)
PCL disappearance02/02 (Lorenc et al. 2003)
04/02 (Harvey & Recely 2002)
Disappearance of PCF
Cycle 21
3
3
North South
Northern HL(NHL)
Disappearance of PCF
Polar field reversal: 02/82- 03/82 (Webb et al.1984)
09/80 & 07/82 from data.
PCL disappearance ① Webb et al. 1984
② Lorenc et al. 2003
①②
HL CME peaklight blue shadow region
Cycle 21
3
3
North South
Southern HL(SHL)
Disappearance of PCF
Polar field reversal: 09/80 (Webb et al. 1984)
02/83 from data.
PCL disappearance ① Webb et al. 1984
② Lorenc et al. 2003
① ②
HL CME peak(pink shadow region)
SummaryThe epochs of solar polar reversal are closely related to the cessation of HL CME activities.
Before the completion of the reversal, several temporary reversals take place with corresponding spikes in the HL CME rates.
The North-South asymmetry of the polarity reversal time and HL activity is of high importance. The CME process helps the closed field lines overlying PCFs become open to complete the polarity reversal. (c.f.: Low (1997))