The OEDIPUS-C sounding rocket observed localized plasma density depletions in the topside auroral ionosphere using two Langmuir probes situated on separate subpayloads several hundred meters apart. One probe was biased in electron saturation (+5 V) and the second in ion saturation (-5 V). Both of these measurements are consistent with density depletions of tens of percent. The depletions have cross-field dimensions of tens of meters and occur in regions of VLF hiss, suggesting they are likely signatures of lower hybrid solitary structures. Time delays between event detections on the two subpayloads are consistent with spatially localized structures traversed in succession. The two-point measurements show directly that the cavities extend at least 800 m along the geomagnetic field line, and the apparent electric potential within them is depressed by roughly 0.5 V. ¿ 1999 American Geophysical Union