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Description of the Solar Wind Summary data plot

Description of the Solar Wind Summary Data Plot

John Steinberg Feb 22, 2002

All parameters shown in the Solar Wind Summary plots are determined autonomously by Genesis in onboard flight software, including the boxcar running averages. The boxcar averaging interval is nominally one hour, but can be re-configured to be up to two hours by ground command.

ABOUT SHOCK DETECTION

The label on the upper left hand corner indicates the time of the last shock identification by the onboard Genesis algorithm. Genesis always retains memory of the last time-of-shock. Note that the last shock may have occurred many days previous to the data shown in the present panel.

Vertical lines extending through all the panels indicate a shock detection by Genesis. Please be qware that the shock detection is retrospective: it is based on examination of the data collected over the previous hour. Genesis shock identification typically occurs about 30 minutes after the actual time of shock passage. Thus, the vertical shock line as well as the shock time label in the upper left hand corner are typically later by about 30 minutes than the actual time of shock passage.

ABOUT THE COLOR-CODED REGIME INDICATOR BAR

Across the top of the plot, the regime determined by the Genesis algorithm is shown as a color-coded bar:

Yellow = Slow inter-stream solar wind

Blue = Coronal Hole fast solar wind

Red = Coronal Mass Ejection solar wind

Gray = Regime Unknown (occurs for short intervals when algorithm is re-initialized)

Be aware that the goal of the Genesis algorithm is to expose the collection samples to the correct flow regime nearly all of the time, but not precisely all of the time. With that in mind, the algorithm regime may often exhibit latency relative to what an experienced observer recognizes as a clear change in the flow conditions. This behavior is built in for several reasons. First, Genesis is constrained to limit the total number of sample array changes during the mission in order to limit the number of times the array motors are operated. To meet this requirement, the Genesis algorithm has hysteresis and persistence built in. In addition, bias has been introduced to keep the Coronal Hole collection most pristine, while allowing the CME collection to accept the most cross-exposure.

 

CONTENT OF PLOT PANELS - TOP TO BOTTOM

Speed Panel

The solar wind proton speed.

White Points

speed at approximately 2.5 minute resolution

White Dotted Line

boxcar running average speed

Temp Panel

The solar wind proton one-dimensional moment temperature Tp

White Points

Tp at approximately 2.5 minute resolution

White Dotted Line

boxcar running average Tp

Green Points

Tp-expected calculated onboard from the speed.

(Tp-expected is, roughly, the most probable temperature for the given solar wind speed. Excursions of Tp below Tp-expected are signatures of some CMEs)

Tex/Tp Panel

The ratio of the Tp-expected to Tp

Green Points

Tex/Tp at the 2.5 minute time resolution

Green Dotted Line

boxcar running averages of Tex/Tp.

(Large values of Tex/Tp are signatures of some CMEs)

Density Panel

The solar wind proton number density.

White Points

proton density at approximately 2.5 minute resolution

White Dotted Line

boxcar running average of the proton density

He ratio Panel

The ratio of the alpha particle number density to the proton number density

White Points

alpha/proton ratio at approximately 2.5 minute resolution

White Dotted Line

boxcar running average of alpha/proton ratio

To_CME Panel

CME Indicator

To_CME is the output parameter of a fuzzy logic scheme to determine the likelihood that measured solar wind is coronal mass ejection related. Higher values indicate greater likelihood of CME detection. The algorithm takes into account the presence or absence of bi-directional electron signatures, the proton temperature as compared with the expected proton temperature for the given speed, and the alpha particle to proton relative abundance ratio. The running averages are used in all cases. When To_CME is greater than a threshold value, then the CME regime is selected. The threshold is nominally 0.4, but can be re-configured via ground command.

White Solid Line

To_CME

BDE Panel

Bi-Directional (or counter-streaming) Electron indicator

Red Hash Marks

At each 2.5 minute data cycle, the BDE parameter is assigned a value of one or zero, depending on whether or not the measured electron spectrum shows the characteristics of bi-directional electron streaming.

Red hash marks indicate a positive indication (BDE=1).

White Solid Line

Running box car average of the value of BDE. At each data cycle, BDE is zero or one. Thus the running average is a value between zero and one.

Questions?

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