Plasma depletion layer: the role of the slow mode waves
The plasma depletion layer (PDL) is a layer on the sunward side of the magnetopause with lower plasma density and higher magnetic field compared to their corresponding values in the upstream magnetosheath. The depletion layer usually occurs during northward (IMF) conditions with low magne...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2004-12-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/22/4259/2004/angeo-22-4259-2004.pdf |
| _version_ | 1818163552949633024 |
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| author | Y. L. Wang J. Raeder C. T. Russell |
| author_facet | Y. L. Wang J. Raeder C. T. Russell |
| author_sort | Y. L. Wang |
| collection | DOAJ |
| description | The plasma depletion layer (PDL) is a layer on the sunward side of the magnetopause with
lower plasma density and higher magnetic field compared to their corresponding values in the upstream magnetosheath.
The depletion layer usually occurs during northward (IMF) conditions with low magnetic shear across the magnetopause.
We have previously validated the Raeder global model by comparing the computed formation of
a magnetosheath density depletion with in-situ observations.
We also have performed a detailed force analysis and found the varying roles that different MHD forces
play along the path of a plasma parcel flowing around the magnetopause.
That study resulted in a new description of the behavior of magnetosheath magnetic flux tubes which
better explains the plasma depletion along a flux tube.
The slow mode waves have been observed in the magnetosheath and have been used to explain the formation of the PDL
in some of the important PDL models.
In this study, we extend our former work by investigating the possible role of
the slow mode waves for the formation of the PDL, using global MHD model simulations.
We propose a new technique to test where a possible slow mode front may occur in
the magnetosheath by comparing the slow mode group velocity with the local flow velocity.
We find that the slow mode fronts can exist in certain regions in the magnetosheath under certain solar wind conditions.
The existence and location of such fronts clearly depend on the IMF.
We do not see from our global simulation results either the sharpening of the slow mode front into a slow mode shock
or noticeable changes of the flow and field in the magnetosheath across the slow mode front,
which implies that the slow mode front is not likely responsible for the formation of the PDL, at least for the
stable solar wind conditions used in these simulations.
Also, we do not see the two-layered slow mode structures shown in some observations and proposed in certain PDL models.
Instead, we see only a one-layered spatial PDL structure under the stable solar wind conditions used in this study. |
| first_indexed | 2024-12-11T16:51:23Z |
| format | Article |
| id | doaj.art-869284bdfdfe4ac1b951cd9fa2c6d2e4 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-11T16:51:23Z |
| publishDate | 2004-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-869284bdfdfe4ac1b951cd9fa2c6d2e42022-12-22T00:58:05ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762004-12-01224259427210.5194/angeo-22-4259-2004Plasma depletion layer: the role of the slow mode wavesY. L. Wang0J. Raeder1C. T. Russell2Los Alamos National Laboratory, Los Alamos, USAUniversity of New Hampshire, Durham, USAUniversity of California, Los Angeles, USAThe plasma depletion layer (PDL) is a layer on the sunward side of the magnetopause with lower plasma density and higher magnetic field compared to their corresponding values in the upstream magnetosheath. The depletion layer usually occurs during northward (IMF) conditions with low magnetic shear across the magnetopause. We have previously validated the Raeder global model by comparing the computed formation of a magnetosheath density depletion with in-situ observations. We also have performed a detailed force analysis and found the varying roles that different MHD forces play along the path of a plasma parcel flowing around the magnetopause. That study resulted in a new description of the behavior of magnetosheath magnetic flux tubes which better explains the plasma depletion along a flux tube. The slow mode waves have been observed in the magnetosheath and have been used to explain the formation of the PDL in some of the important PDL models. In this study, we extend our former work by investigating the possible role of the slow mode waves for the formation of the PDL, using global MHD model simulations. We propose a new technique to test where a possible slow mode front may occur in the magnetosheath by comparing the slow mode group velocity with the local flow velocity. We find that the slow mode fronts can exist in certain regions in the magnetosheath under certain solar wind conditions. The existence and location of such fronts clearly depend on the IMF. We do not see from our global simulation results either the sharpening of the slow mode front into a slow mode shock or noticeable changes of the flow and field in the magnetosheath across the slow mode front, which implies that the slow mode front is not likely responsible for the formation of the PDL, at least for the stable solar wind conditions used in these simulations. Also, we do not see the two-layered slow mode structures shown in some observations and proposed in certain PDL models. Instead, we see only a one-layered spatial PDL structure under the stable solar wind conditions used in this study.https://www.ann-geophys.net/22/4259/2004/angeo-22-4259-2004.pdf |
| spellingShingle | Y. L. Wang J. Raeder C. T. Russell Plasma depletion layer: the role of the slow mode waves Annales Geophysicae |
| title | Plasma depletion layer: the role of the slow mode waves |
| title_full | Plasma depletion layer: the role of the slow mode waves |
| title_fullStr | Plasma depletion layer: the role of the slow mode waves |
| title_full_unstemmed | Plasma depletion layer: the role of the slow mode waves |
| title_short | Plasma depletion layer: the role of the slow mode waves |
| title_sort | plasma depletion layer the role of the slow mode waves |
| url | https://www.ann-geophys.net/22/4259/2004/angeo-22-4259-2004.pdf |
| work_keys_str_mv | AT ylwang plasmadepletionlayertheroleoftheslowmodewaves AT jraeder plasmadepletionlayertheroleoftheslowmodewaves AT ctrussell plasmadepletionlayertheroleoftheslowmodewaves |