The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREO
On 15–17 February 2008, a CME with an approximately circular cross section was tracked through successive images obtained by the Heliospheric Imager (HI) instrument onboard the STEREO-A spacecraft. Reasoning that an idealised flux rope is cylindrical in shape with a circular cross-section, best...
| Main Authors: | , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2009-11-01
|
| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/27/4349/2009/angeo-27-4349-2009.pdf |
| _version_ | 1811198312906227712 |
|---|---|
| author | N. P. Savani A. P. Rouillard A. P. Rouillard J. A. Davies M. J. Owens R. J. Forsyth C. J. Davis R. A. Harrison |
| author_facet | N. P. Savani A. P. Rouillard A. P. Rouillard J. A. Davies M. J. Owens R. J. Forsyth C. J. Davis R. A. Harrison |
| author_sort | N. P. Savani |
| collection | DOAJ |
| description | On 15–17 February 2008, a CME with an approximately circular cross
section was tracked through successive images obtained by the Heliospheric
Imager (HI) instrument onboard the STEREO-A spacecraft. Reasoning that an
idealised flux rope is cylindrical in shape with a circular cross-section,
best fit circles are used to determine the radial width of the CME. As part
of the process the radial velocity and longitude of propagation are
determined by fits to elongation-time maps as 252±5 km/s and 70±5°
respectively. With the longitude known, the radial size is calculated
from the images, taking projection effects into account. The radial width of
the CME, S (AU), obeys a power law with heliocentric distance, <I>R</I>, as the CME
travels between 0.1 and 0.4 AU, such that S=0.26 <I>R</I><sup>0.6±0.1</sup>. The
exponent value obtained is compared to published studies based on
statistical surveys of in situ spacecraft observations of ICMEs between 0.3
and 1.0 AU, and general agreement is found. This paper demonstrates the new
opportunities provided by HI to track the radial width of CMEs through the
previously unobservable zone between the LASCO field of view and Helios in
situ measurements. |
| first_indexed | 2024-04-12T01:29:18Z |
| format | Article |
| id | doaj.art-211125b823a34c838bc130e2c60625b4 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-04-12T01:29:18Z |
| publishDate | 2009-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-211125b823a34c838bc130e2c60625b42022-12-22T03:53:32ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762009-11-01274349435810.5194/angeo-27-4349-2009The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREON. P. Savani0A. P. Rouillard1A. P. Rouillard2J. A. Davies3M. J. Owens4R. J. Forsyth5C. J. Davis6R. A. Harrison7The Blackett Laboratory, Imperial College London, UKSpace Environment Physics Group, School of Physics and Astronomy, Southampton University, Southampton, UKSpace Science and Technology Department, Rutherford Appleton Laboratory, Chilton, UKSpace Science and Technology Department, Rutherford Appleton Laboratory, Chilton, UKThe Blackett Laboratory, Imperial College London, UKThe Blackett Laboratory, Imperial College London, UKSpace Science and Technology Department, Rutherford Appleton Laboratory, Chilton, UKSpace Science and Technology Department, Rutherford Appleton Laboratory, Chilton, UKOn 15–17 February 2008, a CME with an approximately circular cross section was tracked through successive images obtained by the Heliospheric Imager (HI) instrument onboard the STEREO-A spacecraft. Reasoning that an idealised flux rope is cylindrical in shape with a circular cross-section, best fit circles are used to determine the radial width of the CME. As part of the process the radial velocity and longitude of propagation are determined by fits to elongation-time maps as 252±5 km/s and 70±5° respectively. With the longitude known, the radial size is calculated from the images, taking projection effects into account. The radial width of the CME, S (AU), obeys a power law with heliocentric distance, <I>R</I>, as the CME travels between 0.1 and 0.4 AU, such that S=0.26 <I>R</I><sup>0.6±0.1</sup>. The exponent value obtained is compared to published studies based on statistical surveys of in situ spacecraft observations of ICMEs between 0.3 and 1.0 AU, and general agreement is found. This paper demonstrates the new opportunities provided by HI to track the radial width of CMEs through the previously unobservable zone between the LASCO field of view and Helios in situ measurements.https://www.ann-geophys.net/27/4349/2009/angeo-27-4349-2009.pdf |
| spellingShingle | N. P. Savani A. P. Rouillard A. P. Rouillard J. A. Davies M. J. Owens R. J. Forsyth C. J. Davis R. A. Harrison The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREO Annales Geophysicae |
| title | The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREO |
| title_full | The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREO |
| title_fullStr | The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREO |
| title_full_unstemmed | The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREO |
| title_short | The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREO |
| title_sort | radial width of a coronal mass ejection between 0 1 and 0 4 au estimated from the heliospheric imager on stereo |
| url | https://www.ann-geophys.net/27/4349/2009/angeo-27-4349-2009.pdf |
| work_keys_str_mv | AT npsavani theradialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT aprouillard theradialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT aprouillard theradialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT jadavies theradialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT mjowens theradialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT rjforsyth theradialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT cjdavis theradialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT raharrison theradialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT npsavani radialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT aprouillard radialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT aprouillard radialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT jadavies radialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT mjowens radialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT rjforsyth radialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT cjdavis radialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo AT raharrison radialwidthofacoronalmassejectionbetween01and04auestimatedfromtheheliosphericimageronstereo |