A Study of Long-Term Heliospheric Brightness Using SMEI Data

The Solar Mass Ejection Imager (SMEI) has been returning white-light photometric maps of nearly the entire sky with a 102-minute cadence for well over eight years. When the usual sidereal and zodiacal backgrounds are removed, the residual maps are used to study CME/ICME events. Moreover, the successful sidereal subtraction provides a certification of SMEI's photometric accuracy over this time period. Further, since the zodiacal background removal employs a brightness model which does not vary with time, a search for potential long-term changes in the residue can show whether the zodiacal cloud's dust distribution varies within this portion of the present solar cycle. We present results from studies using SMEI imagery along with a concluded zodiacal-light model.