Investigating the Hiss Occurrence Rate as a function of IMF Clock Angle

Investigating the Hiss Occurrence Rate as a function of IMF Clock Angle:

We would like to explain a number of features of the hiss occurrence rate noticeable from the figures above. These six key features are listed as follows:

1. Prenoon hiss corresponds with negative IMF By. It is most apparent in the small to large negative Bz cases as seen from the IMF Clock Angle plot. This observation is also supported by the superposed epoch analysis.

2. Postnoon hiss is, instead, favored by positive IMF By and this is most apparent for small IMF Bz cases. 

3. There are double peaks in the hiss occurrence rate on the nightside of the Earth as seen from the IMF Clock Angle figure (i.e. postnoon hiss is apparently separated from the premidnight hiss by a small minima at dusk)

4. A relatively wider Null at noon separates the prenoon hiss from the postnoon hiss 

5. Premidnight hiss is associated with negative IMF By and also has a high correlation with the negative IMF Bz. 

6. There are very few occurrences of the postmidnight hiss but the superposed epoch analysis show that these events are favored by positive IMF By.