"AVADA KEDAVRA," an unforgivable curse from the Harry Potter series, is the most talked about topic on Twitter for the second day in a row.

Science fiction film The "Last Airbender" is also back in the charts and trending in second place on the morning of August 4 while " Inception," a science fiction film that has become a regular fixture in Twitter's trending topics, moves down one place to number seven.

Third, fourth and sixth places are taken by the memes "#honestyhour," "#hhsjfnvmsdfnjf" (a hashtag being used to replace random words in people's posts) and "#thingsthatbotherme."

American TV series " Pretty Little Liars" is trending in fifth place after it aired on American TV on Tuesday evening.

Email-centric smartphone maker Research In Motion debuted the BlackBerry Torch on August 3 and Twitter users are discussing if the handset is a worthy rival for the likes of the iPhone and Android-powered handsets already available in the market.

Feelings about the new touchscreen slider were mixed in the Twittersphere with users commenting; "The new bb torch looks serious!!! touch screen with a retractable querty keyboard! New Blackberry OS 6! 5 megapixel camera! & it looks sexy," "BlackBerry Torch looks good. Like a hybrid between new iPhone and a BlackBerry. Fortunately unlike the iPhone you'll be able to make calls" and "Torch doesn't impress. If you're buying a phone, get one running Android OS."

People in some areas of the US were treated to a rare sky show of Northern Lights overnight. People are hitting Twitter to share what they saw, pushing "Northern Lights" into the ninth position on Twitter's charts, just ahead of the abbreviation of the word clear, "CLR."

The top 10 most talked about topics on Twitter on August 4 at 9:30 AM GMT are:

1. AVADA KEDAVRA (unchanged)
2. Last Airbender (new)
3. #honestyhour (-1)
4. #hhsjfnvmsdfnjf (new)
5. Pretty Little Liars (re-entry)
6. #thingsthatbotherme (-3)
7. Inception (-1)
8. BlackBerry Torch (new)
9. Northern Lights (new)
10. CLR (-2)