Guest solarfett Posted October 29, 2015 Share Posted October 29, 2015 Great to be here! Im trying to work out where the terms "positive" and "Negative" polarity of CH HSS"s are derived from when used in a solar wind forecast from noaa/swpc etc? I first thought that they were a reference to which hemisphere the majority of the CH occupied ( eg: nth/neg - sth/pos ) though now im wondering if it has more to do with the polarity of the IMF and which side of the heliospheric sheet it is situated on the sun or if its to do with which side it is on when the stream arrives at earth? Any info would be greatly appreciated Link to comment Share on other sites More sharing options...
Vancanneyt Sander Posted October 29, 2015 Share Posted October 29, 2015 The Sun is a big magnet with a northpole and southpole with magnetic connections along them. With coronal holes the magnetic lines are open and the solar wind can escape. These field lines can stretch out far in space and that's what we call the interplanetary magnetic field. Just as magnets we have field lines going away and towards the Sun: On the left image above, you'll also see a coronal hole on a sector boundary crossing where the field changes from toward to away.So when it's in a negative sector (-) that means that the magnetic field lines of the Sun that stretch out far into our solar system are going towards the Sun. When we are in a positive sector, that means that the magnetic field lines of the sun are going away from the Sun. So in the graph there is a representation of the model that predict the polarity of the IMF if it is positive (+ Away) or negative (- towards) and thus know if the coronal hole is in a negative polarity sector or not. "At about 13/0650Z, the phi angle changed from a negative (toward) orientation to a positive (away) orientation, indicating a solar sector boundary crossing. This was followed by increases in density, temperature, and solar wind speed indicative of a co-rotating interaction region in advance of a coronal hole high speed stream (CH HSS)." Also of note: a negative sector in the IMF has nothing to do with the direction of the IMF. So it doesn't mean that a nagtive polarity CH will bring us southward directed magnetic field. Link to comment Share on other sites More sharing options...
Guest Stephane Mabille Posted October 30, 2015 Share Posted October 30, 2015 good GONG Magnetogramme polarity negativ coronale hole Link to comment Share on other sites More sharing options...
Guest solarfett Posted November 4, 2015 Share Posted November 4, 2015 Thanks so much for taking the time to reply :D Also lets use the current positive polarity CH18 as an example. Being situated trans equatorial does the HSS stay within the boundary and follow the positive sector for the entire journey to earth or does the heliospheric sheet cross the stream at any stage? Link to comment Share on other sites More sharing options...
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