Opinions and Comments

Any opinions and comments are welcomed. They will be reflected to the formal document 'SciRD for JMO/EJSM'.


  • TEXT ( Name, e-mail address ( ## AT $$ ) : DD/MM/YY)

Many of us agree that imaging and simultaneous sampling of the solar wind is of critical importance for the success of JMO. However, the orbit requirements must be consistent with the measurement requirement. The following simple orbit requirements have to be kept in mind: (1) Apogee has to be at sufficiently large distance to be able sample the solar wind for an reasonably extended period of time, but not too far away in order to maximize the spatial resolution of the imaging instruments; (2) Perigee must not be too deep in the magnetosphere, since the enormous radiation levels will severely limit the available mass for instruments.

(Pontus C. Brandt, pontus.brandt at jhuapl.edu, JHU/APL, 28/08/08)

From the point of view of the simulation study, the imaging measurements are very useful. It is easy to compare the simulation results with the imaging results because the images have more spatial information than results of in situ measurements (of course I don't deny the in situ measurements). So it may be possible that the imaging interact with the simulation such as the assimilation in Jupiter.

I also mention the importance of IMF not only the dynamic pressure. In our simulation results the direction of IMF (By and Bz) controls the configuration of outer Jovian magnetosphere even though the magnitude of IMF is very small. In some cases they make an influence to the middle/inner magnetosphere. These are probably related to the emission of high (maybe middle) latitude aurora. From some observations results the solar wind varies between the observation of ACE satellite and in front of the Earth (Geotail observation). Thus the solar wind monitoring needs to be located near the Jupiter as possible. Also we need more study of the most suitable location for the solar wind monitoring.

(Ed. Keiichiro Fukazawa, fukazawa AT nict.go.jp : July 30 2008)

Imaging of aurora from high latitude/polar orbiter would be interesting observation. This would enable us the clear division between Local Time (LT) effect and magnetic longitudinal structure. In our numerical model which solves Hill-Pontius equation under current conservation, the field-aligned current shows the daily (LT) variation along the change of solar EUV incident through positive feedback of the ionospheric conductance. In addition, this overcomes the limb effect which causes the mapping accuracy down. This monitoring could be the valuable tool for interpreting some part of auroral variation.

(Chihiro Tao, tao AT pat.geophys.tohoku.ac.jp : 29/07/08)

I also agree and strengthen the importance of solar wind monitoring. Sometimes the lack of the solar wind monitoring is overcome by the one-dimensional MHD propagation of the solar wind measured at the Earth. The assumption that the solar activity is steady state on time scales within a solar rotation expands the solar wind prediction term. The solar activity, however, varies within short time. In the comparison between the solar wind simulation and observation around 5 AU using the Ulysses data in 1998 and 1999, the some pressure enhancements are see only in observation (i.e., simulation can not predict) and vice versa. This means there would be ~29 % ambiguity in the event selection. We found the prediction error in the shock arrival time is ~24 hours. When the error and the duration of pressure pulses are comparable, we cannot identify the increasing or decreasing phase of solar wind dynamic pressure. The real solar wind monitoring would largely improve our discussion without above limitation.

(Chihiro Tao, tao AT pat.geophys.tohoku.ac.jp : 29/07/08)

Fukazawa is right in stressing the importance of solar wind monitoring. Remote measurements, such as ENA imaging and auroral imaging, while in the solar wind have proven very valuable for Cassini. There were a few instances when Cassini was in the solar wind and remotely imaged the energetic ion population in ENAs. Increases in solar wind dynamic pressure could be related to all onsets of intense magnetospheric storm injections/energizations.

(Pontus Brandt, pontus.brandt@jhuapl.edu, 01/07/08)

A lot of magnetospheric dynamics observed by the past spacecrafts at Jupiter, however some of them cannot be discuss the solar wind effects in detail because there are no simultaneous observations of the solar wind and Jupiter (except for the simultaneous observations by Galileo and Cassini). I think this is a serious issue to specify the causes of the magnetospheric phenomena are either the solar wind or Jovian internal processes. For example, in the simulation the variation of both the solar wind dynamic pressure and the inner plasma source affects the configuration of corotation region. The corotation region increases when the dynamic pressure decreases or the inner plasma source increases. In seeing the simulation results, it seems to be difficult to distinguish which is dominant by the observation without the solar wind information. Thus I think it is an essential for the progress of Jovian magnetospheric study to monitor the upstream solar wind even though not the steady observation.

(Ed. Keiichiro Fukazawa, fukazawa AT nict.go.jp : July 1 2008)

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Last-modified: 2008-08-28 (Thu) 19:08:46 (3731d)