The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations
The solar maximum solar wind is highly structured in latitude, longitude and in time. Coronal measurements show a very high degree of variability, with large variations that are less apparent within in situ spacecraft measurements. Interplanetary scintillation (IPS) observations from EISCAT, coverin...
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ftdoajarticles:oai:doaj.org/article:c675cdd10c0a47908a8a77bf48f54e35 2023-05-15T16:04:33+02:00 The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations A. R. Breen P. Riley A. J. Lazarus A. Canals R. A. Fallows J. Linker Z. Mikic 2002-09-01T00:00:00Z https://doi.org/10.5194/angeo-20-1291-2002 https://doaj.org/article/c675cdd10c0a47908a8a77bf48f54e35 EN eng Copernicus Publications https://www.ann-geophys.net/20/1291/2002/angeo-20-1291-2002.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-20-1291-2002 0992-7689 1432-0576 https://doaj.org/article/c675cdd10c0a47908a8a77bf48f54e35 Annales Geophysicae, Vol 20, Pp 1291-1309 (2002) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2002 ftdoajarticles https://doi.org/10.5194/angeo-20-1291-2002 2022-12-31T01:11:50Z The solar maximum solar wind is highly structured in latitude, longitude and in time. Coronal measurements show a very high degree of variability, with large variations that are less apparent within in situ spacecraft measurements. Interplanetary scintillation (IPS) observations from EISCAT, covering distances from 20 to 100 solar radii ( R S ), are an ideal source of information on the inner solar wind and can be used, therefore, to cast light on its evolution with distance from the Sun. Earlier comparisons of in situ and IPS measurements under solar minimum conditions showed good large-scale agreement, particularly in the fast wind. In this study we attempt a quantitative comparison of measurements made over solar maximum by EISCAT (20–100 R S ) and the Wind and Ulysses spacecraft (at 215 R S and 300–1000 R S , respectively). The intervals studied were August–September 1999, May 2000, September 2000 and May 2001, the last-named being the period of the second Ulysses fast latitude scan. Both ballistic and – when possible – MHD/ballistic hybrid models were used to relate the data sets, and we compare the results obtained from these two mapping methods. The results of this study suggest that solar wind velocities measured in situ were less variable than those estimated from IPS measurements closer to the Sun, with the greatest divergence between IPS velocities and in situ measurements occurring in regions where steep longitudinal velocity gradients were seen in situ. We suggest that the interaction between streams of solar wind with different velocities leads to "smoothing" of solar wind velocities between 30–60 R S and 1 AU, and that this process continues at greater distances from the Sun. Key words. Interplanetary physics (solar wind plasma; sources of the solar wind; instruments and techniques) Article in Journal/Newspaper EISCAT Directory of Open Access Journals: DOAJ Articles Annales Geophysicae 20 9 1291 1309 |
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Directory of Open Access Journals: DOAJ Articles |
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topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
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Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 A. R. Breen P. Riley A. J. Lazarus A. Canals R. A. Fallows J. Linker Z. Mikic The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
The solar maximum solar wind is highly structured in latitude, longitude and in time. Coronal measurements show a very high degree of variability, with large variations that are less apparent within in situ spacecraft measurements. Interplanetary scintillation (IPS) observations from EISCAT, covering distances from 20 to 100 solar radii ( R S ), are an ideal source of information on the inner solar wind and can be used, therefore, to cast light on its evolution with distance from the Sun. Earlier comparisons of in situ and IPS measurements under solar minimum conditions showed good large-scale agreement, particularly in the fast wind. In this study we attempt a quantitative comparison of measurements made over solar maximum by EISCAT (20–100 R S ) and the Wind and Ulysses spacecraft (at 215 R S and 300–1000 R S , respectively). The intervals studied were August–September 1999, May 2000, September 2000 and May 2001, the last-named being the period of the second Ulysses fast latitude scan. Both ballistic and – when possible – MHD/ballistic hybrid models were used to relate the data sets, and we compare the results obtained from these two mapping methods. The results of this study suggest that solar wind velocities measured in situ were less variable than those estimated from IPS measurements closer to the Sun, with the greatest divergence between IPS velocities and in situ measurements occurring in regions where steep longitudinal velocity gradients were seen in situ. We suggest that the interaction between streams of solar wind with different velocities leads to "smoothing" of solar wind velocities between 30–60 R S and 1 AU, and that this process continues at greater distances from the Sun. Key words. Interplanetary physics (solar wind plasma; sources of the solar wind; instruments and techniques) |
format |
Article in Journal/Newspaper |
author |
A. R. Breen P. Riley A. J. Lazarus A. Canals R. A. Fallows J. Linker Z. Mikic |
author_facet |
A. R. Breen P. Riley A. J. Lazarus A. Canals R. A. Fallows J. Linker Z. Mikic |
author_sort |
A. R. Breen |
title |
The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations |
title_short |
The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations |
title_full |
The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations |
title_fullStr |
The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations |
title_full_unstemmed |
The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations |
title_sort |
solar wind at solar maximum: comparisons of eiscat ips and in situ observations |
publisher |
Copernicus Publications |
publishDate |
2002 |
url |
https://doi.org/10.5194/angeo-20-1291-2002 https://doaj.org/article/c675cdd10c0a47908a8a77bf48f54e35 |
genre |
EISCAT |
genre_facet |
EISCAT |
op_source |
Annales Geophysicae, Vol 20, Pp 1291-1309 (2002) |
op_relation |
https://www.ann-geophys.net/20/1291/2002/angeo-20-1291-2002.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-20-1291-2002 0992-7689 1432-0576 https://doaj.org/article/c675cdd10c0a47908a8a77bf48f54e35 |
op_doi |
https://doi.org/10.5194/angeo-20-1291-2002 |
container_title |
Annales Geophysicae |
container_volume |
20 |
container_issue |
9 |
container_start_page |
1291 |
op_container_end_page |
1309 |
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1766400131159031808 |