PDA

View Full Version : Solar winds - lack of



MG1962A
2006-Nov-09, 09:05 AM
I am having a discussion with someone about the sun and all that good stuff. Anyway they are convinced that they heard sometime in 98 or 99 that solar winds stop being generated for three days (As per NASA)

I have searched high and low on the net. Tried every possible way of googling the question - but found nothing.

Anyone heard this? Or can direct me to a website where I can browse through some data to see if there is anything behind this story?

As usual, thanks in advance

tusenfem
2006-Nov-09, 09:34 AM
On 11 May 1999 an event took place that in literature came to be known "The day the solar wind almost disappeared".

Here (http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&db_key=PHY&qform=PHY&aut_logic=OR&author=&ned_query=YES&sim_query=YES&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=AND&title=day+solar+wind+disappeared&txt_logic=OR&text=&nr_to_return=100&start_nr=1&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1) you can find al the scientific references in ADS.

Just as an example here is the abstact (publicly available) of a GRL paper by Guan Le et al., to give you an impression of how and what.



We have examined magnetic field data from Polar MFE to study the magnetospheric current systems on May 11, 1999, when the solar wind density was well below 1 cm-3 and the IMF was generally weakly northward. We find that the magnetosphere was much more dipolar than usual but the ring current did not disappear. In the inner magnetosphere, the residual field, the observed magnetic field at Polar with the internal field removed, was dominated by the ring current contribution. The magnetic field data agreed well with the Tsyganenko 1996 model with a weak ring current but little magnetopause current. Weak field-aligned currents were observed both in the northern and southern hemisphere on May 11, as expected for northward IMF. The cusp signature of a depressed magnetic field, normally seen by Polar when passing through the high altitude polar cusp, was not seen on May 11, indicating that the energy density of the plasma in the cusp was much smaller than usual, as would be expected if the solar wind source were of lower density.


And one more solar wind like from a JGR paper by Charles Smith et al.



On May 11, 1999, the Advanced Composition Explorer (ACE) spacecraft observed a rarefied parcel of solar wind. This has come to be known as ``The Day the Solar Wind Disappeared.'' Little if any change is seen in the large-scale interplanetary magnetic field during this time, but the magnetic field fluctuations are depressed and significantly more transverse to the mean field. The high Alfvén speed resulting from the constant field intensity and low ion density enhances wave refraction, and we examine this as a possible explanation for the fluctuation properties. The solar wind possesses a very low proton β, thereby separating the cyclotron and ion inertial length scales and permitting a test of possible dissipation dynamics. We find that the test favors the ion inertial scale theories.


I have not worked on this event, so unfortunately I cannot give you any first hand information, but I am sure you can find more, now that you have the ADS references.

astromark
2006-Nov-09, 09:57 AM
The solar winds fluctuate. It is entirely reasonable for reduced output to be noted and detected just as sudden increases in solar flares and thus extra Aurora activity suggests increased activity of the solar winds. To sagest that it would or might stop completely is unreasonable. You will not find a lot of data on these events because they are merely the normal fluctuations of the solar cycle.
If we were to note a sudden decrease in solar activity and a noticeable drop in solar energy outputs......, I think we might notice. Sit up straight and, then panic.!

MG1962A
2006-Nov-09, 09:58 AM
I have not worked on this event, so unfortunately I cannot give you any first hand information, but I am sure you can find more, now that you have the ADS references.

Absolutely :) And thank you very much

MG1962A
2006-Nov-09, 10:02 AM
The solar winds fluctuate. It is entirely reasonable for reduced output to be noted and detected just as sudden increases in solar flares and thus extra Aurora activity suggests increased activity of the solar winds. To sagest that it would or might stop completely is unreasonable. You will not find a lot of data on these events because they are merely the normal fluctuations of the solar cycle.
If we were to note a sudden decrease in solar activity and a noticeable drop in solar energy outputs......, I think we might notice. Sit up straight and, then panic.!


I totally agree, thats why I was puzzled by the reference. But now I have tusenfem's excellent information. I can now work out exactly what did happen