One possible plotline could be Harry's reasons for jumping. Maybe he's under the influence of a dark spell and jumps to break free from it. Another could be that he jumps as a sacrifice to save his friends, believing it's the only way.
In this type of fanfiction, there could be a plotline where Harry jumps because he's been tricked. Some dark force could have made him believe that his presence at Hogwarts is endangering everyone. So, he decides to sacrifice himself by jumping. However, when he jumps, he actually enters a different dimension or time - a parallel Hogwarts perhaps. There, he has to figure out how to get back and also stop the real threat to his world.
Voldemort could be involved too. It could be part of his plan to drive Harry to despair and jump. Or, on the other hand, Harry's jump could be a way to outwit Voldemort. For example, by faking his death in this way and then coming back stronger to defeat him.
A scenario could be that the Astronomy Tower is a portal to another dimension during a full moon. Only those with a pure heart can enter it. Ginny discovers this and she enters with Neville. Inside the other dimension, they find a world where magic is used in completely different ways and they have to learn new spells to get back home.
One interesting astronomy tower fanfiction could be about an astronomer making a discovery from the astronomy tower. Maybe they spot a new comet while observing from that high vantage point. It could involve the character's excitement, the process of verifying the discovery, and how it changes their life.
One great Astronomy Tower fanfiction could be about a secret midnight meeting there. Maybe Harry and his friends discover a hidden passage in the tower that leads to a room filled with ancient magical artifacts. They have to keep it a secret from the teachers and the other students, especially Malfoy who they suspect might try to steal the artifacts for the wrong reasons.
Well, it depends on the context of the fanfic. If he jumps, he could be in a situation where he believes it's the only way to escape a powerful dark force on the tower. However, his Gryffindor courage might also lead to an unexpected rescue. For example, a phoenix could swoop in and carry him to safety at the last moment.
He could die. In most scenarios, jumping from such a height would be fatal, which would have a huge impact on the wizarding world. His friends like Ron and Hermione would be devastated.
One possible reason could be to save someone else. Maybe a friend or a loved one is in danger at the base of the tower and Harry believes jumping is the quickest way to reach them. For example, if there's a dark spell about to be cast on Hermione and the only way to stop it in time is for Harry to reach her instantly.
I'm not sure of specific authors who only write astronomy tower fanfiction. But you could start by looking at general science - fiction or fantasy authors who might have works that involve astronomy towers. Some well - known science - fiction authors might include Isaac Asimov. He often wrote about scientific concepts and could potentially have something related in his works.
Well, there are fanfictions that deal with the tower being a portal to other magical realms. Imagine Harry and his friends stumbling upon a hidden doorway in the tower that leads to a world full of strange and wonderful magic. There could also be stories where the tower has its own sentient magic, and it starts to act up and cause chaos in Hogwarts. Fanfictions might also explore the idea of a hidden school within the tower, where only the most talented students are secretly taught advanced magic.
One interesting plotline could be exploring Harry's true magical origin in more depth. Maybe he has some ancient magic in his bloodline that was previously unknown. Another could be how his birth affects the entire wizarding world's future in a different way than in the original series.